The Demon Inside
by GiroGirl723
Summary: Written for NaNoWriMo '14. When Castiel wrapped his arms around Dean that fateful night in the bunker, everyone believed it was over. Dean was human again. But that wasn't really the case. Dean, in fact, wasn't as cured as he, sam, and Cas thought. With the Mark bothering him more than ever, Dean will plummet into a darkness he has never experienced before. Rated for dark themes.
1. Prologue

_Well, heya, guys! Sorry I haven't been able to update for a while. Homework got crazy... I changed schools... lots of stuff. But I'm back, and boy do I have news for you._  
><em>I'm doing NaNoWriMo!<em>  
><em>Yep! Fifty thousand words in a month. Probably. So hopefully I'll be able to get a fanfic done for once in my life! This is done from quite a few points of view (it's made obvious from the beginning that Sam, Dean, and Cas are some of them, but expect a few more) and set a month after the events of Sole Survivor.<em>  
><em>Anyway, sit back, relax, and enjoy the ride!<em>

**Prologue**

_Sam_

"You look worried, fellas."

Those were my brother's first words.

Now, before you start to argue that no kid would ever talk like that… he wasn't a kid. In fact, technically those weren't the first words he had ever spoken.

But they were his first words as a human again.

Now I know you're probably pretty confused. I would be too- at least, I would be if I lead a normal, apple-pie life. But see, I don't. Because when your family hunts monsters… well, you learn to process a lot of weird things.

Anyway, I think I have somewhat of a right to be relieved, maybe even happy. Make a big deal out of my brother's "first words as a human again", you know?

Because let me tell you… nothing, absolutely nothing, can prepare you for finding out your brother is a demon.

_Castiel_

"You look worried, fellas."

Those were the most wonderful words I had heard in a long, long time. And believe me- "long" holds a different meaning when you've been in existence for three thousand years. But seeing Dean's face, devoid of the pain and the bloodlust- well, it had been since before he had taken on the Mark of Cain that I had seen him so at ease, and that felt like centuries ago.

It had been a tense moment, watching him wake up after we had given him the last injection of sanctified blood. The black eyes clearing, the holy water… it was all a process of caution that Sam and I both knew was completely and utterly necessary given the circumstances.

But then that smile. The smile that belonged to the old Dean, the human Dean, the Dean I knew so well. And I knew- well, at least I hoped- that everything would be alright.

_Dean_

"You look worried, fellas."

When I said those words, I wasn't able to make sense of much. My memories of the past few months had been a blur. The only thing I knew was Cas and Sam were standing in front of me, with nervous looks on their faces that quickly spread to joy.

It was when I realized the wetness on my face was holy water that I remembered.

Things had been tense. I mean, I had tried to kill my own brother. The worst part was hearing him talking with Cas. Making some excuse to get away from me, something about getting drunk that made my insides clench.

It broke my heart to hear it.

Later on, Cas came to visit me. He and I… we had a good talk. To be honest… it was nice. Us, one-on-one. Spending time, even if it was just a little bit. It felt like old times- until Cas mentioned something about a woman in the car, and my stomach turned, and he gave a sad smile.

"Heaven and Hell are reasonably in order," he had said before he had left. "It's quiet out there."

And I was left wondering if things between us would ever really be the same.


	2. Chapter One: Of Lincolns and Chevys

_Castiel_

My drives now were so different from those in the past.

There were the obvious differences, of course: the Lincoln Continental instead of the Chevy Impala (I was rather proud of my newfound ability to tell the difference between car brands), the fact that I was driving, Hannah as a companion… but there were the little things, too. The jerky putt-putt-putt instead of the steady rumbling of Dean's "baby". The absence of the smell of hamburgers. The silence, instead of the constant stream of classic rock. And there was no familiarity.

It was nice to have a car, of course. Convenient. But the Impala… it was more than just a car. It had memories along with it, fond memories I didn't want to let go of, memories the Lincoln just didn't have.

I stroked my thumb along the smooth leather of the steering wheel, contemplating my situation- which, to be fair, was very complicated at the moment. My Grace was failing, and in turn I was dying. Dean still had the Mark of Cain. And while I had dealt with worse, I couldn't help wishing that for once in my extremely long life that things could be simple. Could be relaxing.

Next to me, my companion furrowed her brow. "Are you feeling alright? Do you need me to drive?" she asked.

"I'm fine, Hannah," I responded. "I don't need to be coddled."

"Coddled, no," she replied, "but we do have to be careful. Your Grace-"

"-has been replenished by Adina's. I will be fine," I said firmly, keeping my eyes on the road. "Right now what matters is-"

"-bringing the rogue angels back to heaven, I know," Hannah finished. "And you're sure you're up to it?"

"I'm fine," I reiterated.

Hannah pursed her lips.

We drove in silence for a while, watching the road go by. A sign proclaimed that "Council Bluffs, IA" was in 5 miles, and I sighed in relief. We were almost there.

"So… review," I said after we passed the sign.

"Pardon?" Hannah queried.

I sighed. "When humans have a task to do, they usually go over said task before completing it."

She looked at me skeptically. "You really have changed."

The corner of my lip twitched. "Being human does that to you.

Hannah shot me a look. "But you are human no longer, Castiel. And we need to focus on getting your Grace back, you know that."

I exhaled. "I know. Now can we please review?"

Hannah gave a resigned sigh. "Very well. We're tracking down an angel named Amitiel."

"Angel of truth," I said.

"Yes," she confirmed. "She was one of the first angels to go rogue, but as she does see reason very easily I'm sure we can convince her to come back."

I wanted to point out that reason and truth weren't always the same thing, but determined it unwise. Instead I pressed on the accelerator, and it took us a matter of minutes to reach the outskirts of Council Bluffs.

We pulled up in a small trailer park on the edge of the city. It was fairly deserted; most likely due to lack of convenience. Too close to the city to enjoy nature yet too far away from its center to do much of anything without a fair drive; not the most ideal locale.

Unless you were a rogue angel in hiding, I suppose.

Hannah and I got out of the car cautiously, glancing around. "Which trailer?" I asked.

She glanced at me worriedly. "Third trailer on the left. You couldn't tell?"

"Of course I could," I rectified quickly, not wanting her to realize my Grace had already faded to the point where I could barely sense other angels.

She narrowed her eyes but didn't push the topic further; instead, she materialized her angel blade and I followed suit. We cautiously approached the dilapidated trailer, on guard as usual.

It was a sorry sight. The metal walls were dented and tarnished by rust, one side sinking lower than the other. The stairs to the front door- although they looked more like a section taken off of bleachers- seemed ready to fall apart at any minute, and the windows were bolted shut. All of it made for a very pitiful picture.

We had barely made it to the would-be stairs when the door cracked open and a young woman- twenty-two or twenty-three at the most- peered out wearily, piercing blue eyes reflecting centuries of turmoil. It would seem out of place to a human given the tiny girl in front of us; to any angel it showed her to be one of our own.

"I knew you would come for me eventually," was all she said. "You might as well come in."


End file.
